Image display apparatus and method

Abstract

A light source emits a light having a luminance. A light source luminance decision unit determines the luminance for a frame of the image based on pixel values of the frame. A conversion unit converts each pixel value of the frame in correspondence with the luminance. A light modulation unit displays the image by modulating a transmittance or a reflectance of the light based on each converted pixel value of the frame. A selection unit selects a timing to change the luminance in a display period of the frame by comparing the luminance for the frame with a luminance for a previous frame. A control unit changes the luminance of the light source to the luminance for the frame at the timing.

1 . An apparatus for displaying an image, comprising:
 a light source configured to emit a light having a luminance;   a light source luminance decision unit configured to determine the luminance for a frame of the image, based on pixel values of the frame;   a conversion unit configured to convert each pixel value of the frame in correspondence with the luminance;   a light modulation unit configured to modulate a transmittance or a reflectance of the light based on each converted pixel value of the frame to display the image;   a selection unit configured to select a timing to change the luminance in a display period of the frame by comparing the luminance for the frame with a luminance for a previous frame; and   a control unit configured to change the luminance of the light source to the luminance for the frame at the timing.   
   
   
       2 . The apparatus according to  claim 1 , wherein
 the selection unit calculates a difference by subtracting the luminance for the previous frame from the luminance for the frame, selects a first timing that a first period has passed from a start timing to write the frame onto the light modulation unit if the difference is smaller than a first threshold, and selects a second timing that a second period longer than the first period has passed from the start timing if the difference is larger than the first threshold.   
   
   
       3 . The apparatus according to  claim 2 , wherein
 the first threshold is zero, and   the selection unit selects the first timing if the difference is positive value, and selects the second timing if the difference is negative value.   
   
   
       4 . The apparatus according to  claim 3 , wherein
 the selection unit sets the first timing for a next frame by delaying the second timing for the frame as one frame period.   
   
   
       5 . The apparatus according to  claim 3 , wherein
 the selection unit selects a third timing that a third period longer than the first period and shorter than the second period has passed from the start timing, if an absolute value of the difference is smaller than a second threshold.   
   
   
       6 . The apparatus according to  claim 2 , wherein
 the selection unit controls the timing to pass a longer period from the start timing if the difference is larger.   
   
   
       7 . The apparatus according to  claim 1 , further comprising:
 a detection unit configured to detect a scene change between the frame and the previous frame, based on pixel values of the frame and pixel values of the previous frame;   wherein the selection unit selects the timing based on a difference between the luminance for the frame and the luminance for the previous frame, if the detection unit detects the scene change.   
   
   
       8 . The apparatus according to  claim 2 , further comprising:
 a detection unit configured to detect a scene change between the frame and the previous frame, based on pixel values of the frame and pixel values of the previous frame;   wherein the selection unit selects the first timing or the second timing based on the difference if the detection unit detects the scene change, and selects a third timing within a period between the first timing and the second timing if the detection unit does not detect the scene change.   
   
   
       9 . The apparatus according to  claim 2 , further comprising:
 a detection unit configured to detect a scene change between the frame and the previous frame, based on pixel values of the frame and pixel values of the previous frame;   wherein the selection unit selects the first timing or the second timing based on the difference if the detection unit detects the scene change, and selects a third timing within a period between the first timing and the second timing if the detection unit does not detect the scene change.   
   
   
       10 . The apparatus according to  claim 7 , wherein
 the selection unit selects the second timing, if the detection unit detects the scene change and if the difference is larger than a second threshold.   
   
   
       11 . An apparatus for displaying an image, comprising:
 a plurality of light sources configured to respectively emit a light having a luminance, each light source being set in correspondence with each region on a frame of the image;   a light source luminance decision unit configured to determine the luminance of a light source, based on pixel values of a region corresponding to the light source;   a conversion unit configured to convert each pixel value of the region in correspondence with the luminance of the light source;   a light modulation unit configured to modulate a transmittance or a reflectance of the light from the light source, based on each converted pixel value of the region;   a selection unit configured to select a timing to change the luminance in a display period of the region by comparing the luminance for the region with a luminance for a corresponding region on a previous frame; and   a control unit configured to change the luminance of the light source to the luminance for the region at the timing.   
   
   
       12 . A method for displaying an image, comprising:
 determining a luminance of a light source based on pixel values of a frame of the image;   converting each pixel value of the frame in correspondence with the luminance;   modulating a transmittance or a reflectance of a light from the light source, based on each converted pixel value of the frame;   selecting a timing to change the luminance in a display period of the frame by comparing the luminance for the frame with a luminance for a previous frame; and   changing the luminance of the light source to the luminance for the frame at the timing.